Originally Posted by: magicninjaSo taking the C major scale. 2-->denotes higher octave

C D E F G A B C2 D2 E2 F2 G2 A2 B2 C2

CEGB would be Cmaj7?

CEGD2 would be Cmaj9?

and so on and so forth?

Would adding any octave of B to CEG make it Cmaj7?

Sort of...Ninth chords also have the sevenths.

CEGBD or CEBD would be C9

Any octave? Yes, I mean, you want to thresh out the voices a little bit so that the B and C aren't right next to each other, unless you're going for a tense, cramped chord. You could have them 6 octaves apart if you really wanted, but the distance would make it sound a bit goofy if not done well.

yeah, after 9ths come 11ths

Which are just 1-3-5-7-9-11. Then 13ths which are 1-3-5-7-9-11-13 which is the entire scale haha.